Apparatus for controlling the fuel air ratio for internal combustion engines



July 4. 1967 F. F. OFFNER 3,329,411

APPARATUS FOR CONTROLLING THE FUEL AIR RATIO FOR INTERNAL COMBUSTION ENGINES Filed May 5, 1965 x INVENTOR Fran/(L in F Offner BY JWXlPWAM 17 ATTORNEYS United States Patent 3,329,411 APPARATUS FOR CONTROLLING THE FUEL AIR RATIO FOR INTERNAL COMBUSTION ENGINES Franklin F. Offner, 1890 Telegraph Road, Bannockburn, Deer-field, Ill. 60015 Filed May 5, 1965, Ser. No. 453,330 12 Claims. (Cl. 261-27) This invention relates to an improved apparatus for controlling the fuel flow in an internal combustion engine, and more particularly to an improved means for controlling the fuel-air ratio in such engines employing positive displacement fuel pumping means, as exemplified by injection-type engines.

In any internal combustion engine it is necessary to control the flow of fuel and of air in such ratio as to insure efiicient combustion; and in such total quantity as to deliver the desired power.

In fuel injection engines, the quantity of fuel supplied is usually determined by the setting of a positive displacement pump, whose delivery of fuel per engine revolution may be set by some means: e.g., by varying the stroke of the pump. The amount of fuel pumped is then proportional to the delivery per stroke, times the r.p.m. of the engine.

The quantity of air delivered to the cylinders is more diflicult to determine. It will be a function of the position of the air throttling member (e.g., butterfly valve), the air temperature, the air pressure, and the rpm. of the engine. In the past, it has been the practice to measure all these variables, and to combine them in a fuel control device in such a manner as to approximate the desired fuel-air ratio flow. Such devices have suffered from the disadvantages of being quite complex in construction, difiicult to adjust, and of being of only approximate accuracy.

The present invention solves the problem in a Simple, reliable, and accurate means, resulting in at the same time a less costly and improved performance engine.

The invention to be described herein employs the method of ionizing radiation for measuring the air density, as disclosed in my United States Letters Patent No. 2,739,478; but whereas said previous patent was particularly adaptable to engines employing continuous flow of fuel and of air (e.g., ram jets), the present invention is adapted to piston type engines.

Having disclosed the general purposes of my invention, I will now describe it in detail, with the aid of several figures. In the accompanying figures:

FIGURE 1 illustrates the invention as applied to an internal combustion engine.

FIGURE 2 illustrates a modified form of throttle control.

FIGURE 3 illustrates a combined direct and electronic throttle control linkage.

FIGURE 4 illustrates an alternative means of controlling the air density signal.

FIGURE 5 illustrates means for correcting the signal developed by the air density, to compensate for various factors.

FIGURE 6 illustrates another version of the control, in which air and fuel control means are reversed as compared to FIG. 1, and which further incorporates additional control features.

Referring now to FIGURE 1 of the drawings, 1 represents the cylinder of an internal combustion engine, 2, the piston, and 3 the intake valve. The fuel-air mixture is conducted to the cylinder through intake manifold 4, with fuel injected through nozzle 5 just before the intake valve. Alternatively, the fuel may be injected directly into the cylinder, as in direct injection engines. The fuel is metered by injection pump 6, driven through shaft 7,

3,329,411 Patented July 4, 1967 "ice which is in turn driven from the crankshaft of the engine. The quantity of fuel delivered per stroke of the pump is set by the position of control lever 8, which controls the effective stroke of the pump in one of several ways well known to the art. Fuel is supplied to the injection pump from reservoir 9, it being understood that other usual fuel system components (pump, filter, etc.) may be interposed.

The flow of air into manifold 4 is controlled by throttle valve 10, whose position is in turn controlled by solenoid 11. In the manifold 4, or alternatively, in a separate chamber communicating therewith, is ionizing air density measuring means 12. This consists of electrode 13, electrically insulated from the manifold, and to which a high voltage V is applied; and electrode 14, also insulated, and which is connected to amplifier means 15, through coupling resistor 16 and balancing voltage potentiometer 17. The output of amplifier I5 is connected to solenoid 11.

Means for ionizing the air between the electrodes is provided within 12. This may be a radioactive coating on electrode 13, for example. A suitable material is the element polonium; or preferably a form of radium which will continually form polonium, and thus maintain the strength constant.

The position of electrode 13 relative to 14 can be changed in accordance with the motion of power control lever 18, which at the same time displaces electrode 13, and pump stroke control lever 8. A cam 19 may be interposed, so that the distance between 13 and 14 is reciprocally related to the stroke of pump 6. That is, if D represents the distance between 13 and 14, and S, the stroke of the pump, then D is proportional to l/S: D=k -1/S. If now D is small enough compared to the path length of the ionizing particles that the number of ion pairs per unit length of path is constant; and if the voltage V applied is suflicient to sweep up all ion pairs formed before recombination occurs, then, as was shown in my aforesaid Patent 2,739,478, the current I through electrode 14 will be proportional to the air density p times D: I =k Dp.

In a piston engine, operating at good volumetric efiiciency, the volume of air entering the cylinder is proportion-al to the rpm. of the engine. Therefore the Weight of air entering is proportional to the rpm. times the air density:

where M is the mass flow of air per minute and N is the rpm.

Combining these equations gives where k =k k /k Since the rate of fuel flow is NS, the current I is thus proportional to the ratio of mass air flow, to fuel flow, the quantity which it is desired to control.

The voltage at the input to the amplifier is IR, where R is the resistance of element 16. This'voltage is balanced against the voltage tapped from potentiometer 17, at the desired fuel-air ratio, and thus 17 is the setting control for fuel-air ratio. As a matter of fact there must be a small unbalance to produce the current to actuate solenoid 11. With amplifier 15 a high gain amplifier, the unbalance is small.

In operation, power is changed by moving lever 18, which changes the rate of fuel fiow to the engine. The motion of electrode 13 simultaneously results in a change in the input to the amplifier, causing throttle 'valve 10 to open or close as required, to reestablish balance. If fuel fiow were increased, the engine speed would then start to increase, causing an increased air flow through the manifold. This would decrease the air density therein, and thus cause the throttle valve to open, to reestablish again balance at the amplifier input.

To achieve rapid operation and still maintain stability, amplifier 15 may include integrated feedback, as disclosed in my United States Letters Patent No. 3,082,954.

Rather than to employ a solenoid at 11, a motor may be employed. In FIGURE 2 an electric motor 21 is shown operating valve 10. With a motor, balance is reestablished at essentially zero amplifier input, eliminating droop characteristics. In place of the electric motor, an pneumatic motor or piston, controlled through electrically actuated valves, could equally well be employed.

When the power control lever is rapidly moved, throttle valve 10 rapidly take on its new position to maintain the fuel-air ratio at its desired value. The amount of correction required to be given by solenoid 11, or motor 21, may be reduced by having an approximate setting of 11 produced by the motion of 18 directly, the electrical control member then producing only the necessary correction to bring the quantity to its exact desired value. This arrangement is shown in FIGURE 3. Here, 18 and 11 jointly determine the position of valve 10 through member 20. With 11 at a fixed position, the motion of 18 gives 10 its desired position under average conditions. Any departure from the correct value is produced by subsequent motion of 11.

A modified form of the invention is shown in FIG. 4. In this form, electrode 13 remains fixed in position, but resistor 16 is changed in value with the position of 18, by having sliding contact 22 displaced by cam 19 in such a manner that R=k /S, where R is the net effective value of 16. Then andthe voltage developed across the resistor is again proportional to the ratio of mass air flow to fuel flow.

In place of having the variable resistor at the input to the amplifier, it is obviously possible to employ a tapped resistor following a pre-amplifier, so that a lower value of resistor may be employed.

While the apparatus as described will hold constant fuel-air ratio flow with an engine of high volumetric efficiency, at high rpm. the volumetric efficiency may fall off. To compensate for this, a correcting voltage may be introduced into the amplifier input. This may be accomplished as, for example, as shown in FIG. 5. Here, an alternator 23 driven by the engine, applies its output to differentiating circuit composed of capacitor 24 and resistor 25. Thus the voltage across 25 increases rapidly with engine speed. This voltage is rectified by 26, and the voltage developed across resistor 28 is filtered by capacitor 27. This correcting voltage signal is applied to the junction point between feed resistor 29 and potentiometer 17, giving the desired correcting voltage at the amplifier input. Zener, limiting, and threshold diodes may be added in ways well known to the art to further modify the curve of applied voltage vs. speed.

A modification of flow with temperature may also be readily obtained by making one resistor in the circuit temperature sensitive: e.g., resistor 29. If this resistor increases with temperature, it will give rise to a lower air density for balance at higher temperatures; whereas if it decreases, the converse would be true. Numerous alternative positions for such a temperature sensing resistor are obviously possible.

The design of the electrode system 13, 14 may include the refinements of guard ring and shielding, as has been already fully disclosed in my aforesaid Patent No. 2,739,- 478.

It will be recognized that, while the illustrations show only a single cylinder of an engine, the invention is equally applicable to engines with several cylinders. It is also equally applicable to other fields of use where gas flow and liquid flow are to be simultaneously controlled, and where the pumping of each fluid is by means similar to those above described.

The invention is also applicable to any other system of pumping of the two fluids, where one is a liquid and the other a gas, in which the ratio of the volume of the two fluids pumped is determined by the position of a member. Thus, rather than to control the stroke of a pump operating at a fixed speed ratio to the engine, a constant stroke pump, or gear pump, could be employed, and the speed ratio varied. These various possibilities are mentioned only as illustrative of the various ways in which the invention can be applied.

While the invention has been illustrated in an embodiment in which the fuel pump setting is made by the operator, and the air flow is controlled to maintain the desired fuel-air ratio, it is obvious that the converse arrangement can be employed; that is, the throttle valve 10 can be set, and the control can adjust the setting of the fuel pump to maintain the desired fuel-air ratio. Such an arrangement has the operating advantage that the operator may not set a fuel fiow beyond the capacity of the engine to adjust to the desired fuel-air ratio. The embodiment of FIGURE 1 may be modified to achieve this configuration by changing operating lever 18 to actuate valve 10; and changing the connection of solenoid 11 to actuate cam 19 and control lever 8..

Cam 19 has been described as producing a motion of electrode 13 reciprocally related to the stroke of the fuel pump, in order to obtain constant fuel-air ratio. In some instances constant ratio may not be desired under all operating conditions, and the cam form may be modified to achieve this. For example, it is usually desired to operate at a higher fuel-air ratio at maximum throttle. The cam may be so cut as to so modify the fuel-air ratio at full pump stroke.

Alternatively the position of valve 10 may be used to modify the fuel-air ratio setting at its extreme open position, or when approaching this position. This may be accomplished either by a switch closure, or preferably by the use of a variable resistor connected to 10. The latter arrangement is shown in FIGURE 6, which illustrates as well the arrangement in which valve 10 is controlled by operating lever 18. Here, as 18 is moved, changing the position of valve 10, wiper tap 30 is moved on variable resistor 31. When the voltage tapped off by 30 exceeds the potential at the junction of resistors 32, 33, current will flow through diode 34, producing a voltage change across resistor 35, and thus introducing a modifying signal voltage into the input of amplifier 15 through resistor 36. The output of amplifier 15 sets fuel pump 6 through an electrically controlled actuating device 37, which could as before be one of the types well known to the art.

When valve 10 is rapidly opened, the air may be allowed to enter the engine so rapidly that the servo system is unable to follow the change, and as a result the fuel-air ratio may become momentarily too low, and the engine may spit back. The converse problem is not likely to be troublesome, since the engine will be more tolerant of excess fuel than of insufficient fuel.

To prevent this type of malfunction, FIGURE 6 includes a ditferentiating circuit composed of capacitor 33 and resistor 39. The voltage appearing across 39 is representative of the speed with which 10 is moved. Diode 40 permits only signals indicating valve 10 being opened to pass, and provides a signal through resistor 41 momentarily increasing the stroke of the fuel pump 6, and thus preventing malperformance from too-lean a mixture.

I claim:

1. Apparatus for controlling the ratio of a liquid flow to a gas flow including, pumping means for said liquid, pumping means for said gas, both of said pumping means being of the positive displacement type, means for varying the delivery rate per revolution of said pumping means for said liquid, means for driving said pumps at a constant speed ratio, an intake manifold for said gas, means for throttling the gas entering said manifold, a pair of spaced electrodes located in a position of communication with the interior of said manifold, means for producing ionization of the gas between said electrodes, electrical polarizing means applied to said electrodes, current measuring means responsive to the current flow between said electrodes, means modifying the output of said current measuring means in accordance with a change in delivery rate of said liquid pumping means, and means responsive to said modified output of said current measuring means for adjusting the relation between the position of said throttling means and the delivery rate of said liquid pumping means.

2. Apparatus for controlling the ratio of a liquid flow to a gas flow including, pumping means for said liquid, pumping means for said gas, both of said pumping means being of the positive displacement type, means for driving said pumps at a constant speed ratio, an intake manifold for said gas, means for throttling the gas entering said manifold, a pair of spaced electrodes located in a position of communication with the interior of said manifold, means for producing ionization of the gas between said electrodes, electrical polarizing means applied to said electrodes, current measuring means responsive to the current flow between said electrodes, means for varying the delivery rate per revolution of said liquid pumping means, means responsive to the setting of said delivery rate varying means for modifying the output of said current measuring means, and means for adjusting said throttling means in response to the modified output of said current measuring means.

3. Apparatus as defined in claim 2 for controlling the ratio of a liquid flow to a gas flow wherein said means responsive to the setting of said delivery rate varying means for said liquid pumping means effects a variation in the spacing between said pair of electrodes to thereby modify the output of said current measuring means.

4. Apparatus as defined in claim 2 for controlling the ratio of a liquid flow to a gas flow wherein said means responsive to the setting of said delivery rate varying means for said liquid pumping means effects a decrease in the output of said current measuring means in accordance with an increase in the delivery rate of said liquid pumping means, and vice versa.

5. Apparatus for controlling the ratio of a liquid flow to a gas flow including, pumping means for said liquid, said pumping means being of the positive displacement type and including means for varying the delivery rate therefrom, pumping means for said gas, said gas pumping means being also of the positive displacement type, means for driving said pumps at a constant speed ratio, an intake manifold for said gas, adjustable throttling means for the gas entering said manifold, a pair of spaced electrodes located in a position of communication with the interior of said manifold, means for producing ionization of the gas between said electrodes, electrical polarizing means applied to said electrodes, current measuring means responsive to the current flow between said electrodes, means controlled in accordance with an adjustment in delivery rate per revolution of said liquid pumping means for modifying the output of said current measuring means, and means responsive to the modified output of said current measuring means for adjusting the position of said means by which the delivery rate of said liquid pumping means is varied.

6. Apparatus as defined in claim 5 for controlling the ratio of a liquid flow to a gas flow wherein said means controlled in accordance with an adjustment in delivery rate of said liquid pumping means for modifying the output of said current measuring means increases the output as said delivery rate is decreased, and vice versa.

7. Apparatus as defined in claim 5 for controlling the ratio of a liquid flow to a gas flow wherein said means for modifying the output of said current measuring means in accordance with an adjustment in delivery rate of said liquid pumping means is constituted by means which adjust the spacing between said pair of electrodes.

8. Apparatus for controlling the flow of fuel and air into an internal combustion engine of the type in which fuel is injected by a positive displacement pump of controllable delivery rate driven at a speed having a fixed ratio to the speed of said engine, and in which the air intake flows through a passageway controlled by a throttling device, said apparatus comprising a pair of spaced electrodes located in a position of communica tion with said air intake passageway, means for producing ionization of the air between said electrodes, electrical polarizing means applied to said electrodes, current measuring means responsive to the current flow between said electrodes, means modifying the output of said current measuring means in accordance with a change in the delivery rate per engine revolution of said fuel pump, and means responsive to the modified output of said current measuring means for adjusting the relation between the position of said throttling device andthe delivery rate of said fuel pump.

9. Apparatus as defined in claim 8 for controlling the flow of fuel and air to an internal combustion engine wherein said means responsive to the output of said current measuring means functions to effect a change in the position of said throttling device.

10. Apparatus as defined in claim 8 for controlling the flow of fuel and air to an internal combustion engine wherein said means responsive to the output of said current measuring means functions to effect a change in the delivery rate of said fuel pump.

11. Apparatus as defined in claim 8 wherein the output of said current measuring means is modified inversely as the change in delivery rate of said fuel pump.

12. Apparatus as defined in claim 8 wherein said means for modifying the output of said current measuring means is constituted by means which vary the spacing between said pair of electrodes inversely as the change in delivery rate of said fuel pump.

References Cited UNITED STATES PATENTS 2,330,650 9/1943 Weiche 26l50 2,447,267 8/1948 Mock 123-119 2,529,101 11/1950 Orr 26l27 2,592,284 4/1952 Hopkins 12332 2,696,809 12/1954 Muraszew l23-139 2,739,478 3/1956 Olfner 73-196 2,941,524 6/1960 Aldinger et a1. 123-139 HARRY B. THORNTON, Primary Examiner. T. R, MILES, Assistant Examiner. 

1. APPARATUS FOR CONTROLLING THE RATIO OF A LIQUID FLOW TO A GAS FLOW INCLUDING, PUMPING MEANS FOR SAID LIQUID, PUMPING MEANS FOR SAID GAS, BOTH OF SAID PUMPING MEANS BEING OF THE POSITIVE DISPLACEMENT TYPE, MEANS FOR VARYING THE DELIVERY RATE PER REVOLUTION OF SAID PUMPING MEANS FOR SAID LIQUID, MEANS FOR DRIVING SAID PUMPS AT A CONSTANT SPEED RATIO, AN INTAKE MANIFOLD FOR SAID GAS, MEANS FOR THROTTLING THE GAS ENTERING SAID MANIFOLD, A PAIR OF SPACED ELECTRODES LOCATED IN A POSITION OF COMMUNICATION WITH THE INTERIOR OF SAID MANIFOLD, MEANS FOR PRODUCING IONIZATION OF THE GAS BETWEEN SAID ELECTRODES, ELECTRICAL POLARIZING MEANS APPLIED TO SAID ELECTRODES, CURRENT MEASURING MEANS RESPONSIVE TO THE CURRENT FLOW BETWEEN SAID ELECTRODES, MEANS MODIFYING THE OUTPUT OF SAID CURRENT MEASURING MEANS IN ACCORDANCE WITH A CHANGE IN DELIVERY RATE OF SAID LIQUID PUMPING MEANS, AND MEANS RESPONSIVE TO SAID MODIFIED OUTPUT OF SAID CURRENT MEASURING MEANS FOR ADJUSTING THE RELATION BETWEEN THE POSITION OF SAID THROTTLING MEANS AND THE DELIVERY RATE OF SAID LIQUID PUMPING MEANS. 